1. Field of the Invention
This invention relates generally to communication systems, and, more particularly, to Internet Protocol (IP) Multimedia Subsystem (IMS) communication systems.
2. Description of the Related Art
Service providers typically provide numerous voice and/or data services to subscribers using one or more wired and/or wireless communication systems. Exemplary services include cellular telephony, access to the Internet, gaming, broadcasting or multicasting of audio, video, and multimedia programming, and the like. Mobile subscriber units such as cell phones, personal data assistants, smart phones, pagers, text messaging devices, global positioning system (GPS) devices, network interface cards, notebook computers, and desktop computers may access the services provided by the communication systems over an air interface with one or more base stations. Communication between mobile units and base stations are governed by various standards and/or protocols, such as the standards and protocols defined by the 3rd Generation Partnership Project (3GPP, 3GPP2).
The service providers use offline and online billing functions to keep track of the charges incurred by each subscriber unit for using the various services provided by the service provider. The 3GPP standards group has defined a set of specifications that may be used to implement online charging systems and offline charging systems to cover charging in the various network domains (e.g., a circuit switching network domain, a packet switching network domain, and/or a wireless domain), IP multimedia subsystems, and emerging 3G application services. Offline charging is generally defined as a charging mechanism where charging information does not affect, in real-time, the service rendered. In offline charging, charging information for network resource usage is collected concurrently with that resource usage. Online charging is generally defined as a charging mechanism where charging information can affect, in real-time, the service rendered, and therefore a direct interaction of the charging mechanism with session/service control is needed. In online charging, charging information for network resource usage is collected concurrently with that resource usage in the same fashion as in offline charging. However, authorization for the network resource usage must be obtained by the network prior to the actual resource usage to occur.
FIG. 1 conceptually illustrates a charging architecture 100 as defined by the 3GPP. The charging architecture 100 may be found in the technical specification 3GPP TS 32.240. The left part of FIG. 1 illustrates the offline charging system 102 of the charging architecture 100. Offline charging system 102 includes a Charging Data Function (CDF) 110 and a Charging Gateway Function (CGF) 112. The right part of the FIG. 1 illustrates the online charging system (OCS) 104 of the charging architecture 100. The detailed functional components of online charging system 104 may be found in the technical specification 3GPP TS 32.296. Offline charging system 102 and online charging system 104 both transmit charging data records (CDR) to a billing system 106. A CDR is a formatted collection of information about a chargeable event (e.g. time of call set-up, duration of the call, amount of data transferred, etc) for use in billing and accounting. A separate CDR is generated for each party to be charged for parts of (or all) charges of a chargeable event. More than one CDR may therefore be generated for a single chargeable event, e.g. because of its long duration and/or because more than one charged party is to be charged for the event.
Offline charging system 102 communicates with the following elements or functions to receive charging information: a circuit-switched network element (CS-NE) 121, a service network element (service-NE) 122, a SIP application server (AS) 123, Multimedia Resource Function Control (MRFC) 124, Media Gateway Control Function (MGCF) 125, Break out Gateway Control Function (BGCF) 126, Proxy-Call Session Control Function (CSCF)/Interrogate-CSCF (I-CSCF) 127, Serving-CSCF (S-CSCF) 128, Wireless LAN (WLAN) 129, SGSN 130, GGSN, 131, and Traffic Plane Function (TPF) 132. These elements and functions are known to those familiar with the 3GPP specifications. Online charging system 104 communicates with the following elements or functions to receive charging information: circuit-switched network element (CS-NE) 121, service network element (service-NE) 122, SIP application server 123, MRFC 124, S-CSCF 128, Wireless LAN (WLAN) 129, SGSN 130, GGSN, 131, and Traffic Plane Function (TPF) 132. These elements and functions are known to those familiar with the 3GPP specifications.
FIG. 2 conceptually illustrates online charging system 104 as defined by the 3GPP. Online charging system 104 includes Online Charging Functions (OCF) 202. Online charging functions 202 include Session-Based Charging Function 204 and Event-Based Charging Function 206. Online charging system 104 further includes an Account Balance Management Function (ABMF) 208, an online Rating Function (RF) 210, and a Charging Gateway Function (CGF) 212. These elements and functions are known to those familiar with the 3GPP specifications.
FIG. 3 conceptually illustrates a generalization of the charging architecture 100 as defined by the 3GPP to show the operation of the charging architecture 100. Charging architecture 100 includes a Charging Trigger Function (CTF) 302, offline charging system 102, online charging system (OCS) 104, and billing system 106. Both offline charging system 102 and online charging system (OCS) 104 introduce a charging gateway function, which are the charging gateway function (CGF) 112 and the charging gateway function (CGF) 212, respectively. Charging gateway function 112 and charging gateway function 212 both act as gateways between the network and the billing system 106 to provide CDR pre-processing functionality. Offline charging system 102 includes a charging data function (CDF) 110 and charging gateway function 112. Online charging system 104 includes online charging function (OCF) 202, account balance management function (ABMF) 208, an online rating function (RF) 210, and charging gateway function 212. Billing system 106 includes offline rating function (RF) 304.
According to the 3GPP standards, the charging trigger function 302 is the focal point for collecting the information pertaining to chargeable events within a network element (not shown). The charging trigger function 302 in one or more network elements generates charging information for one or more calls. Depending on subscriber provisioned charging characteristics, a charging trigger function 302 transmits offline charging information to the charging data function 110 via an Rf interface 310. A charging trigger function 302 transmits online charging information to online charging system 104 via an Ro interface 311. The online charging system 104 and the offline charging system 102 are typically implemented in parallel. Once the charging information has been received from the charging trigger function 302, the online charging system 104 and the offline charging system 102 operate in different and distinct manner, at least in part because of the different and distinct specifications for online and offline charging.
For offline charging, the charging data function 110 receives the offline charging information for a call or a call session. The charging data function 110 generates a charging data record (CDR) based on the offline charging information. The CDR is unrated at this point. The charging data function 110 transmits the unrated CDR to charging gateway function 112 via Ga interface 312. Charging gateway function 112 preprocesses the unrated CDR, such as for validation, consolidation, error-handling, etc, and filters the unrated CDR. Charging gateway function 112 also temporarily buffers the unrated CDR. Responsive to a request from billing system 106, charging gateway function 112 transmits the unrated CDR to billing system 106 via Bx interface 313, e.g., using the File Transfer Protocol (FTP). The “x” subscript for the Bx interface 313 may be a “c”, “p”, “i”, “l”, “m”, “o”, “w”, etc, depending on the network domain. For instance, “c” represents Circuit Switched (CS), “p” represents Packet Switched (PS), “i” represents IP Multimedia Subsystem (IMS), “l” represents Location Service, “m” represents Multimedia Message Service (MMS), “o” represents Online Charging System (OCS), and “w” represents Wireless LAN (WLAN). The billing system 106 includes an offline rating function 304 for determining the rate for offline charging of calls. Billing system 106 accesses the offline rating function 304 to determine a rate for the unrated CDR, and generates a rated CDR for the offline charging of the call session.
For online charging, online charging function 202 includes a session-based charging function 204 and an event based charging function 206 (see FIG. 2). Each function contains a charging data function to generate CDRs. An online charging function 202 (or its corresponding charging data function) receives online charging information from a charging trigger function 302 for a call session. Responsive to the online charging information, online charging function 202 accesses online rating function 210 to determine a rate for the call session associated with the online charging information. The online charging function 202 generates a rated CDR based on the rate for the call session and the online charging information, and transmits the rated CDR to charging gateway function 212 for CDR pre-processing via Ga interface 314, e.g., using the File Transfer Protocol (FTP). Charging gateway function 212 preprocesses the CDRs and filters the preprocessed CDRs. Charging gateway function 212 temporarily buffers the rated CDR. Responsive to a request from billing system 106, charging gateway function 112 transmits the rated CDR to billing system 106 via Bo interface 315.
As discussed above, the existing 3GPP standard specifications treat online charging and offline charging as separate functions that are implemented in parallel. The charging gateway function 112 for the offline charging system 102 can only feed an unrated CDR to the billing system 106 via the Bx interface 313. The billing system 106 thus needs its own independent offline rating function 304 in order to rate offline charges for calls. On the other hand, online charging system 104 includes its own online rating function 210 that rates online charging for calls. The 3GPP standards do not define an interface to enable the charging gateway function 112 for the offline charging system 102 to feed CDRs to online charging system 104 for further rating and balance adjustment. Thus, most service operators need to manage, support, maintain, and update two separate charging systems from different vendors. Maintaining two separate charging systems may increase overhead and reduce the operational efficiency of the communication system.
Cai, et al. (U.S. Pat. No. 7,010,104) describes a pre-biller capability that may be implemented in enhanced charging collection function (CCF) applications. The pre-biller includes an offline charging interface with the online charging system that may be used for call cost calculation based on the CDR. The pre-biller allows the online charging system to calculate costs of offline communications during periods of low online communication, such as off-peak time periods. However, Cai does not specify how the pre-biller controls the time for calculating the call cost at the rating engine or how the online charging system and the rating engine provide the calculated call cost to the pre-biller.